Ch 7.3 Cell Transport Osmosis GizmoName ______

Gizmo Warm-up

A cell membrane is a thin “barrier” that surrounds a cell. It is asemipermeable membrane, which means that some particles pass through the membrane easily while others cannot.

The Osmosis Gizmo™ portrays a cell (red square) in a solution of purple soluteparticles dissolved in green solvent(water) particles. Press Play ( ) and observe.

  1. Which particles CAN pass through the cell membrane?
  1. The cell membrane is PERMEABLE to which particles?
  1. Which particles CANNOT pass through the cell membrane?
  1. The cell membrane is NOT PERMEABLE to which particles?
  1. Click Reset (), and then click Play again. What do you notice about the size of the cell?

Activity A:
Observing osmosis / Get the Gizmo ready:
  • Click Reset. Set the Initial cell volume to 40%.
  • You will need a calculator for this activity.
/

Question: How do solute concentrations affect the volume of a cell?

  1. OBSERVE: Use the Solute outside slider to change the concentration of solute particles outside the cell. Be sure to INCREASE and DECREASE concentration. Click Play. In each case, focus on whether the cell gets bigger or smaller.
  1. In what situation does the cell get larger…MORE or LESS solute outside cell?
  1. In what situation does the cell get smaller…MORE or LESS solute outside cell
  1. CALCULATE: The concentration of a solute is the amount of solute particles in a given amount of solvent. To calculate percentage concentration, divide the number of solute particles by the total number of particles (solute + solvent), then multiply by 100:

% concentration = (solute ÷ total particles) × 100

Select the DESCRIPTION tab. Click Reset. Set the Solute outside to 10 and check the Initial cell volume is 40%. DO NOT CLICK PLAY. ANSWER THE FOLLOWING:

  1. How many solute particles are found inside the cell? ______Outside? ______
  1. How many solvent particles are found inside the cell? ______Outside? ______
  1. What is the % concentration of solute inside the cell? ______
  1. What is the % concentration of solute outside the cell? ______
  1. Has the cell reached HOMEOSTASIS  is it balanced and stable? YES or NO
  1. CIRCLE 3 ANSWERS  Solute concentration is higher (INSIDE or OUTSIDE) cell forcing water to move (INSIDE or OUTSIDE) cell causing it to (EXPAND or SHRINK).
  1. OBSERVE: Now Click PLAY, and observe the numbers shown on the DESCRIPTION pane. How does each number change over time? Write increases, decreases, or stays same.

A) Solute particles inside? ______

B) Solvent particles inside? ______

C)Solute concentration inside? ______

D)Solute particles outside? ______

E)Solvent particles outside? ______

F)Solute concentration outside? ______

  1. OBSERVE: Wait until the numbers are not changing very much. What do you notice about the solute concentrations inside and outside of the cell now?

This situation is called dynamic equilibrium.

  1. EXPERIMENT: Click Reset. Check that the Solute outside is 10 and the Initial cell volume is 40%. To calculate the solvent concentration, divide the number of solvent particles by the total number of particles, and then multiply by 100.
  1. What is the solvent concentration inside the cell?
  1. What is the solvent concentration outside the cell?
  1. Higher solvent concentration is (INSIDE or OUTSIDE) the cell.
  1. Click PLAY. Most of the solvent particles move (INSIDE or OUTSIDE) the cell and it (EXPANDS or SHRINKS).
  1. Is the cell HYPOTONIC or HYPERTONIC?
  1. EXPERIMENT: Click Reset, and set the Solute outside to 1 and cell volume to 40%.
  1. What is the solvent concentration inside the cell?
  1. What is the solvent concentration outside the cell?
  1. Higher solvent concentration is (INSIDE or OUTSIDE) the cell.
  1. Do you think the cell will get larger or smaller?
  1. Click PLAYto confirm your predictions. Were you correct?
  1. Is the cell HYPOTONIC or HYPERTONIC?
  1. SUMMARIZE: You have observed examples of osmosis—the diffusion of water across a semipermeable membrane. Fill in the paragraph with the following terms or phrases:

(EXPAND, SHRINK, LOW, HIGH, OUT OF, INTO)

During osmosis, water moves from an area of ______solvent concentration to an area of ______solvent concentration. When there is a higher concentration of SOLUTE particles inside the cell, water particles will move ______the cell and the cell will ______. When there is a higher concentration of SOLUTE particles outside the cell, water particles will move ______the cell and the cell will ______.

Activity B:
Effect of cell volume / Get the Gizmo ready:
  • Click Reset.
  • Set the Solute outside to 5.
  • Set the Initial cell volume to 40%.
/

Question: How does changing the cell volume affect solute concentrations?

  1. EXPERIMENT: Select the BAR CHART tab, and turn on Show numerical values.
  1. Based on solute concentrations, do you expect the cell to swell or shrink?
  1. Click Play, and observe. Was your prediction correct?
  1. OBSERVE: Click Reset. Keep the solute set at 5. Move the Initial cell volume slider back and forth BIGGER and SMALLER. How does the initial cell volume affect the solute concentrations inside and outside the cell?
  1. Bigger cells have ______solute concentration inside compared to outside.
  1. Smaller cells have ______solute concentration inside compared to outside.
  1. EXPERIMENT: With the Solute outside set to 5, predict whether the cell will swell, shrink, or stay the same with each Initial cell volume settings. Check  Click PLAY.

Predictions:20% ______50% ______60% ______

Actual results:20% ______50% ______60% ______